The present invention relates to an ink composition for ink jet printing and to a method of printing using the same. More particularly, the present invention relates to a phthalocyanine derivative, to an ink composition comprising the same, and to a method for forming color images using the ink compositions and phthalocyanine derivatives of the present invention.
Ink compositions are required to have certain overall properties and performance characteristics. Specifically, they are not only required to have excellent color reproducibility, but also required to produce images that are excellent in water resistance and light resistance. Additionally, in ink jet printing in which droplets of an ink composition are ejected on a recording medium to form an image thereon, the ink composition is required to have more stringent properties than those required for ordinary writing utensils such as fountain pens and ball-point pens. For instance, the ink composition is required to have a proper viscosity and a suitable surface tension, to possess suitable stability and to not cause clogging in a nozzle.
Ink jet printers produce color images by using, in general, yellow, magenta and cyan ink compositions, and optionally a black ink composition. By superimposing these ink compositions, other colors are developed. In such color printing, each ink composition is required to be highly reproducible in its own color. In addition to this, these ink compositions are required to be excellent in reproducibility in red, green, and blue, and optionally black colors which are developed by superimposing ink compositions one over another.
In general, many of these properties required for the ink composition for use in ink jet printing can be satisfied by an aqueous ink composition comprising a water-soluble dye water and a water-soluble organic solvent. The properties of printed images, such as color tone, water resistance and light resistance, are highly dependent on the dye used. It has been tried to utilize various dyes.
Ink compositions containing a phthalocyanine derivative as a cyan or blue dye are known in the art. The use of various phthalocyanine derivatives is disclosed, for example, in U.S. Pat. No. 5,296,023, in U.S. Pat. Nos. 5,704,969, 4,632,703, 5,123,960, and in Japanese Laid-Open Patent Publications Nos. 2772/1986, 149758/1987, 190273/1987 and 200883/1991. However, there is yet room for improvement in these ink compositions containing a phthalocyanine derivative.
In view of the foregoing shortcomings, there is a need in the art for phthalocyanine-containing dyes and ink compositions having desirable performance characteristics (e.g., high chroma, as well as having good ink quality, pen reliability, color tone, water resistance and light resistance). There is a further need for such dyes and ink compositions which possess enhanced performance characteristics, do not require addition of high concentrations of external bases or organic compounds to the ink.
The present invention relates to novel phthalocyanine cyan dyes, ink formulations containing these dyes and methods for ink jet printing with the inks containing the phthalocyanine cyan dyes. The invention provides phthalocyanine cyan dyes having one or more appended chelating arm(s), which induces monomer dye formation and increased chroma. According to the present invention, there is provided phthalocyanine dyes represented by the following formula I: 
wherein
M represents an ion of a metal selected from Cu, Fe, Co, Mg, Mn, Sn and Ni,
X represents a linear compound having 6-10 atoms in length and containing C, O, and/or N,
R1 represents pyridine, imidazole, sulfide, thiol, phenol, benzene, benzaldehyde, pyrimidine, pyrizine, triazine, thiazole, oxazole, pyridone, pyrone, pyrole, thiophene, furan, pyran, dioxane, and morpholine, and derivatives thereof,
R2 represents SO3H, OH, COOH, NH2, COONHR3, COONR3 (where R3 is a substituted or unsubstituted alkyl group that contains a water solubilizing group (such as, e.g., COOH, OH, SO3H, etc.) and the corresponding salts of COOH and SO3H groups (e.g., Na+, K+, NH4+); in addition, these water solubilizing groups can be of the formula Y-X, where Y represents an alkyl group and X represents SO3H, OH, H, COOH, NH2, COONHR, and COONR2 groups (e.g., CH2CH2xe2x80x94SO3H),
y and z each independently represent an integer of 1 to 3 satisfying the relation of 2xe2x89xa6y+zxe2x89xa64.
The invention also provides liquid preparations, cyan ink compositions, and ink sets having cyan inks containing at least one dyestuff of the formula (I).